This study is a prospective longitudinal investigation into the speech-sound production abilities of young patients with a diagnosis of severe traumatic brain injury (TBI). The first two aims of the investigation are to determine the rate and level of consonant mastery over a 12-month period in children who have suffered severe TBI. The third aim is to compare the consonant production errors of children injured earlier (12-48 months of age) and later (49-120 months of age) in the speech development process, after referencing their performance to uninjured age peers. The fourth aim will test multivariate models of five variables predicted to influence the rate and level of consonant mastery in these children. The findings from this research will provide much needed data of the rate and level of speech-sound change of children at various points in the speech development process as well as new information on the variables that predict speech-sound change.